Aperiodic vibrator



2 Sheets-Sheet 1 Filed June 29, 1951 INVENTOR. HAROLD .1. BROWN P 14,1954 H. J. BROWN 2,689,280

APERIODIC VIBRATOR Filed June 29, 1951 2 Sheets-Sheet 2 Q INVENTOR.

HAROLD J. BROWN W as;

Patented Sept. 14, 1954 UNITED STATES PATENT OFFICE Claims.

The invention relates in general to vibrating reed structures and inparticular to the wellknown electromechanical vibrator which has avibrating reed carrying movable contacts wherein provision is made toprevent any appreciable secondary vibration in the movable contacts tothus gain the term aperiodic vibrator.

In general, in the prior art structures, the vibrating reed drivesmovable contacts to cooperate with fixed contacts and the fundamentalfrequency of the vibrating reed is generally lower than the resonantfrequency of the movable contacts. This is principally because thelength of the movable contact arm is less than the length of thevibrating reed for a given mass and compliance. In the past, attemptshave been made to utilize the higher resonant frequency of the movablecontact arms by establishing this frequency at a third or fifthharmonic. Normally, the interval during which the contacts are open issmall compared to the displacement or excursion of the weighted end ofthe vibrating reed. It has been found that as the contacts separate, themovable contacts are accelerated by a transient acceleration which isimparted to the movable contact by reason of its being connected to thevibrating reed. The greater the spacing between the contacts, the morethe contacts have a chance to accelerate before they again reclose andhence again stop movement. In the prior art vibrators, the spacing inthe contacts was sufficiently great that the transient velocity couldbecome much larger than the average velocity, wherein this averagevelocity is that which is obtained by the fact that it is driven fromthe vibrating reed.

Accordingly, it is an object of the invention to provide a vibratorstructure wherein a minimum of energy is transferred to the movablecontacts from the vibrating reed so that there may be a chatter-free orbounce-free closure of the contacts.

Another object of the invention is to provide a vibrator structurewherein the contact spacing is kept to a minimum and wherein thestructure provides the necessary rigidity to maintain this closespacing.

Another object of the invention is to provide a rigid vibrator structureto permit a close spacing of the contacts wherein this spacing is lessthan the displacement of the reed divided by 50a, wherein a is the ratioof the length of the reed to the length of the movable contact arms. 7

Still another object of the invention is to provide a U-shaped frame fora vibrator with a reed disposed parallel to and vibrating into and outof the plane of the U-shaped frame such that a weighted permeable end onthe vibrating reed always maintains a close spacing with the legs of theframe to maintain a magnetic circuit of high efficiency.

Still another object of the invention is to provide a vibrator structurewhich may be assembled easily, is rigid after being assembled, andwhereinthe parts are assembled in a consecutive order to permitadjustment of these parts at the time of assembly rather than having toresort to final adjustment by bending the various parts after assembly.

Still another object of the invention is to provide a method forassembling a vibrator structure wherein a reed sub-assembly is placed inand frictionally held in a U-shaped frame so that this subassembly maybe precisely positioned and then dipped in solder to fasten it in place,and further wherein the fixed contact arms may be next fastened to thelegs of the U-shaped frame and adjusted for spacing and parallelism withthe movable contact arms on the reed sub-assembly.

Other objects and a fuller understanding of my invention may be had byreferring to the following description and claims, taken in conjunctionwith the accompanying drawing, in which:

Figure 1 is a front view of the U-shaped frame and coil mounted in theclosed end;

Figure 2 is a side view of the frame of Figure 1;

Figure 3 is a front view of a reed sub-assemly;

Figure 4 is a side view of the sub-assembly of Figure 3; s

Figure 5 is a front view combining Figures 1 and 3 and including fixedcontact mounting blocks;

Figure 6 is a side view of the assembly of Figure 5;

Figure 7 is a front view of the completely assembled vibrator;

Figure 8 is a side view of Figure '7;

Figure 9 is an enlarged partial view taken on line 9--9 of Figure '7,showing the movable contact on the reed in cooperation with the fixedcontact;

Figure 10 is an isometric view of the fixed contact sub-assembly; and

Figure 11 is a graph showing the velocities of the reed and movablecontact through one cycle 7 of operation.

The complete vibrator II is shown in Figures 7 and 8 and includesgenerally a U-shaped frame I2, a driver coil I3, a reed sub-assembly I4and first and second fixed contact sub-assemblies I5 and I6,respectively. The Figures 1 to 6 show various stages in the assembly ofthe complete vibrator Hence, these may be referred to for betterunderstanding of the components of the various sub-assemblies. TheFigures 1 and 2 show the U-shaped frame I2 which has first and secondlegs I9 and 20, respectively, and a closed end 2|. The Figure 2 showsthat this frame has first notches 22 and second notches 23. The drivercoil I3 has a permeable core 24 which is used to fasten this coil to theclosed end 2| and further has an elongated rectangular head 25. Theframe I2 additionally has a hole 26 adjacent the head 25.

The Figures 3 and 4 show the reed sub-assembly I4 which includesgenerally the flexible vibrating reed 29 having first and secondapertures 30 and 3|. The first aperture 30 adds flexibility to the reedto make it limber and the aperture 3| creates an effective hinge portion32. First and second movable contact arms 33 and 34 are fastened to thereed 29 just above the hing portion 32 by any suitable means such asriveting. These contact arms extend out substantially perpendicular tothe plane of the reed 29. The movable contact arms 33 and 34 areprovided with a silver overlay on the upper side thereof near the tipsto act as the actual contact material.

The lower end of the reed 29 is fastened to first and second bracketarms 35 and 36 by any suitable means, such as riveting. These bracketarms have upturned legs 31 which are disposed substantially parallel inplanes which are perpendicular to the plane of the reed 29. The reed 29also has at the upper end thereof a mass or weight 38 which is permeableand which is attached to the reed by any suitable means, such asriveting.

The Figures 5 and 6 show the reed sub-assembly M in place in the frameI2 and this frame is shown as having contact blocks 40 and 4| at thenotches 22. It will be observed that both contact blocks bridge from oneleg to the other and are fastened to these legs by any suitable means,such as soldering or brazing, or may even be press-fitted into place.The notches 22 thus provide shoulders or abutment means to establishthese contact blocks 40 and 4| in a fixed position.

In the Figures 5 and 6, it will be seen that the reed sub-assembly I4has been positioned in the U-shaped frame with the upturned legs 37 incontact with the inside of the open end of the legs I9 and 20 of theframe I2. These legs 31 give a large bearing surface between the reedsub-assembly I4 and the frame I2 so that this sub-assembly may beaccurately positioned and fastened to the frame such as by soldering.The Figures 5 and 6 further show that the mass or weight 38 ispositioned closely to the head 25 of the core 24. The hole 26 permitsone to observe the off-center position of the mass 38 relative to thehead 25.

The Figure is an isometric view of one of the fixed contactsubassemblies I 5 or I6 and these sub-assemblies are identical. Figure 9also shows the details of this sub-assembly. This sub assembly includesa washer block 44, first and second insulator blocks 45 and 46 with acontact arm 41 sandwiched between these insulator blocks. The contactarm 41 has a terminal ear 48 to provide external electric connection tothe vibrator. The contact arm further has an enlarged hole 49 throughwhich a mounting screw 50 may pass. This mounting screw passes throughapertures in the washer block 44 and the two insulator blocks 45 and 46and because of the insulator blocks and the enlarged hole 45, thecontact arm 41 is electrically insulated from the remainder of the fixedcontact subassembly I5.

The contact arm 41 has a C-shaped portion 5| just below the insulatorblocks 45 and 46 and then a narrow contact foot 52 extends from thisC-shaped portion 5|. The contact foot 52 is disposed at right angles tothe plane of the insulator blocks 45 and 46 and this contact footcarries an electrical contact 53 preferably of a platinum alloy.

The Figures '7 and 8 show the completely assembled vibrator with thefixed contact sub assemblies I5 and I6 mounted on the contact blocks 40and 4| so that the electrical contacts 53 cooperate with the movablecontact arms 33 and 34. The contact blocks 40 and 4| have a threadedaperture 54 to receive the mounting screw 50 and thus provide means tofasten the fixed contact sub-assemblies to the frame I2.

The complete vibrator shown in Figures 7 and 8 is a rigid structurewhich permits the contact spacing to be maintained throughout the lifeof the vibrator even though it is subjected to rough usage and handling.This is effected because the fixed and movable contacts are firmly builtand held in the frame and because the frame itself is a rigid structure.Further the complete vibrator permits the parts of the vibrator to beconsecutively assembled wherein a part is adjusted and firmly fastenedbefore the next part is brought into the assembly. This permits a muchmore rugged structure since the parts are not first assembled and thenadjusted by bending, rather they are adjusted as they are assembled. Themethod of assembly of the complete vibrator starts with the U-shapedframe I2 and then the driver coil I3 is added at the closed end 2|thereof. The core 24 is placed through a hole in the closed end 2| andriveted over to fasten this coil I3 to the frame I2. It will be notedthat the coil I3 is off-center in Figure 2 and further it will be notedthat the rectangular head 25 has the length thereof extending betweenthe legs I9 and 20.

The reed sub-assembly is fabricated in a more or less conventionalmanner by riveting on the weight 38, the movable contact arms 33 and 34,and the bracket arms 35 and 36. Next, this reed sub-assembly I4 isplaced in the frame I2 with the upturned legs 31 in frictionalengagement with the ends of the legs I9 and 20 of the frame I2. TheFigure 1 shows these legs initially bent slightly inwardly and thus thenatural resiliency of these legs I9 and 20 will temporarily hold thereed sub-assembly I4 in any desired position. The reed sub-assembly isnext adjusted longitudinally as seen in Figure 5 for close spacing withthe head 25 and is adjusted laterally as seen in Figure 6 through thehole 26 to place the weight 38 just off to one side of the head 25.After this precise positioning, the open end of the frame I2 may beclipped in molten solder to permanently fasten the reed sub-assembly I4into the frame I2. By this method of assembly, there is thus no dangerof moving the reed sub-assembly I4 relative to the frame I2 after. theprecise positioning, such as might occur if this reed sub-assembly wereto be riveted to the frame I2.

The contact blocks 40 and 4| are next firmly fastened to the frame I2 bypressditting them in place or by brazing and these contact blocks 40 and4| thus provide a firmfoundation for the fixed contact sub-assemblies I5and I6.

Alternatively, the contact blocks 43 and ii could be fastened tortheframe i2 and then the reed sub-assembly I4 could be adjustablypositioned and soldered in position in the frame I2.

Next, the fixed contact sub-assemblies I5 and I6 are fastened to thecontact blocks re and e; by the mounting screws 50. The screws 59 wouldbe turned not quite tight so that the contact arms 41 may belongitudinally adjusted to provide the correct and close spacingrelative to the movable contact arms 33 and 34. Such spacing may beobserved through the notches 23. Upon achieving the correct adjustment,the screws 50 would be tightened.

The contact feet 52 may in some cases need to be bent slightly to obtainparallelism between these feet and the movable contact arms 33 and 34.Since these feet are quite narrow relative to the main body portion ofthe contact arms 47, it will be seen that any bending will occur at theheel of these feet rather than up in the main portion of the contactarrns 4?. This provides that any slight bending will only affect theparallelism and will not change the original distance between theelectrical contacts 53 and the reed 29.

The fact that the contact blocks 46 and 4| bridge the legs I9 and 20provides a rigid frame structure for the vibrator II which will not bebent out of shape by any rough handling and further any such roughhandling will not affect the spacing between the elyectrical contacts 53and the movable contact arms 33 and 34. Further, the large cooperatingsurface areas between the upturned legs 37 and the frame legs I3 and 2!!permit a good soldering bond to be established therebetween so that thereed sub-assembly it cannot move relative to the frame i2. All thisprovides a structure which is very rigid, which will not change itsdimensions during its useful life, and wherein the critical dimensionsare consecutively established and locked in place before the nextcomponent of the vibrator is placed in 1 1e assembly.

The U-shaped frame I2 provides a magnetic circuit of high efiiciencysince the weight 38 extends into close proximity to the legs I9 and 20and because the reed 29 is in a plane parallel to the plane which passesthrough both legs I9 and 20. This means that the excursion or displacement of the weight 38 is not limited by the physical spacingbetween the legs I9 and 20 which would be the case if the reed 29 weredisposed at right angles to the position shown in the drawing. Further,the ends of the weight 38 are in close proximity to the legs I9 and 26)so that the flux lines go down through the core 24, through the head 25,jump the small air gap to the mass 38 and again jump the small air gapsfrom the mass 38 to the legs I9 and 20 to return to the core 24. It istherefore seen that the flux lines do not need to pass through thelength of the vibrating reed 29.

To better understand the novel results obtained, the followingmathematical analysis is offered as a theory of operation. Consider amass M2 which includes the contact arms 33 and 34 and the lower reed.

6 This mass is restrained by the very flexible hinge portion 32 and theinertia of the weight M1, which is principally the weight 38. Further,consider this mass M2 to rotate around an effective pivot, and hence,the frequency of vibration of this mass is where v M2=effective mass ofmovable contacts 33 and Cz=compliance ofmovable contacts 33 and 34.

Also,

where M1=efiective mass of reed 29 and mass 38, C1=comp1iance of reed 29and mass 38.

Also,

will vanish. Since w=21rf, one gets from Equation 1:

For the sake of simplicity, assume a equals 1, which will be reinsertedat the end of the analysis to determine actual dimensions.

When the vibrator contacts separate at the end of a contacting interval,the velocity of the mass M2 due to the fundamental mode of vibration is:

where M =27Ff and P =maximum contact pressure reaction due to Since theprincipal weight M1 moves many times faster than the contact and itsequivalent associated mass, the velocity of this contact portion. of thevibrator will increase according to the relationship:

or: V (1cos a t) (4) where V1 is the velocity of the mass M1, and whereDr, is the transient velocity of the contacts.

The cosine function may be expanded, and if only small angles areinvolved,

2 cos w t=1 Therefore,

2 1 COS w i= 2 Hence:

are plotted for one cycle, with V1 having a maximum amplitude about 10times as great as the maximum amplitude of V2, the velocity of thecontacts 33 and 34, which is the desired condition, since one wants theenergy primarily in the reed 29. Lines 56 and 51 represent the beginningand end or one period of vibration. Lines 58 and 59 represents thebeginning and end of the open contact interval or the period. In thisopen contact interval, or is plotted, since the transient velocitycommences at this point 58. It will be seen that m gets to a maximum ata point 60, and the rest or this curve is shown dotted indicating thepath thereof if this transient velocity were permitted to continue tobuild up. Point 6| shows the instantaneous velocity of V2 when thecontacts reclose. To make sure that the transient m does not affect thevelocity V; appreciably,'so that there is no perceptible change in V1,we will choose t at point 60 to be only one-half V2 at point 6|. Thisone-half value will be used to make a determination of the requiredorder of magnitude.

By substituting Equation 2 into Equation This equation gives thetransient component of velocity in terms of the velocity of the mainweight and the mass of the lower portion of the vibrator and the reedcompliance. It varies as the square of the time.

The velocity Ut which is a function of time may be then equated to theconstant component due to the fundamental frequency f1.

t2 %2C"1=%P2MC2 since the maximum transient velocity or is assumed to beone-half the average velocity V2.

Since V equals S1401 (8) where S equals displacement or excursion ofweight Ml of the reed,

2M,c, o, (9)

The contact pressure P: is determined by:

since it is directly proportional to the excursion of the weight M1 andinversely proportional to the compliance C1 of the reed, assuming anamely, the total spacing of the two contacts, divided by the velocityof the contacts.

Therefore,

28, t equals P2401 C2 (14) by substituting Equation 3 in Equation 13,and

28 6, t equals SW02 by substituting Equation 10 in Equation 14.

8 This is the time taken to cross the gap in terms of the spacing, andother factors it there were no transient efiect. Actually while thistransient affects the velocity, it has small efiect here on thedisplacement.

So the two t's are equated by combining Equations 12 and 15:

Equation 21 is obtained from Equation 20 by reinserting a, which occursin the first power in the ratio of the spacings S1 and S2, and occurs inthe second power in the ratios of the compliances. The expression:

a Cg

is known as the spring ratio, and hence the Equations 21 and 22 give themaximum spacing in terms of the displacement of the mass 38 and thefrequency and spring ratios.

Ordinarily a vibrator of practical design would have a spring ratio offrom 5 to 10 and a frequency ratio as defined under the radical, of thesame order.

Thus the maximum displacement of the vibrator weight will be from 50a to200a times the contact spacing to meet these requirements. Since in mostcases "0. equals 2, or in the present case it equals 2.5, the requiredspacing is of the order of .001" to .002 for an amplitude of S1 equalingabout inch.

Most vibrators have about one-half of this amplitude with .005" or sopractical spacing. It can be seen that the operation of the vibrator His entirely difierent, and that an aperiodic unit is achieved with theclose spacing of S2, while prior art vibrators will be seriouslyaffected by the high frequency harmonics which will be generated byimpulse associated with the off contact velocity transient.

The silver overlay contacts 33 and 34 have a small mass of, say, 30milligrams compared with the prior art tungsten contacts of, say, 300milligrams. This permits the contact mass M2 to be small and thus have ahigh resonant frequency. In accordance with Equation 22, and. the factthat the contact spacing can be made sufiiciently small to keep thetransient velocity in less than half of V2. By examining the curve of min Figure 11, it will be seen that the beginning of this curve follows asquare law. If the contact spacing were made .005", as per prior artpractices, rather than about .002", the transient velocity or would beabout five or six times that presently obtained. Since the energy in amoving system is proportional to the mass times the square of thevelocity, it can be seen that the energy of the driver coil I3 need beonly a small fraction of that in the prior art devices, which generallyrequired about A; to /2 watt. Only about 30 to 50 milliwatts of powerare required for the driver coil 13, or about one-tenth that formerlyrequired. This is due to keeping the transient velocity low, hencekeeping low the resultant or total velocity of the contacts 33 and 34.Since the transient velocity is kept at a value less than the maximum ofV2, there is a negligible effect on V1, and hence an aperiodic vibratoris obtained.

Although the invention has been described in its preferred form with acertain degree of particularity, it is understood that the presentdisclosure of the preferred form has been made only by way of exampleand that numerous changes in the details of construction and thecombination and arrangement of parts may be resorted to withoutdeparting from the spirit and the scope of the invention as hereinafterclaimed.

What is claimed is:

1. A vibratory interrupter for converting a unidirectional current intoan interrupted current comprising a substantially U-shaped permeableframe having an open and a closed end, a driver coil, means for mountingsaid coil in said closed end of said frame, a contact base, means formounting said contact base between said open end of said frame and saiddriver coil, a bracket arm mounted on and extending across said open endof said frame, an armature having first and second ends, means formounts ing said first end of said armature on said bracket arm with saidsecond end of said armature extending toward said closed end of saidframe, said second end of said armature extending in close proximity tosaid coil, at least one spring contact having first and second endsturned substantially at right angles relative to each other, means formounting said first end of said spring contact on said armature withsaid second end thereof extending away from said closed end of saidframe, at least one side arm having first and second ends turnedsubstantially at right angles to each other, means for mounting saidfirst end of said side arm on the outer surface of said contact basewith said second end thereof extending away from said closed end of saidframe, and contact means mounted on said second end of said side arm forcooperating with said second end of said spring contact.

2. A vibratory interrupter comprising a frame having first and secondlegs and a closed end for a substantially U-shaped form having an openend, each of said legs having abutment means thereon, a driver coil,means for mounting said coil on said closed end of said frame, contactbase means having outer surfaces, means for mounting said contact basemeans to said frame abutting said abutment means, a bracket having amain portion extending across said open end of said frame and havingarms perpendicular to said main portion to lie parallel to and engagesaid first and second legs, an armature having first and second ends andhaving a spring hinge portion, means for mounting said first end of saidarmature on said bracket arm with said second end of said armatureextending toward said closed end of said frame, said second end of saidarmature extending in close proximity to said coil, said paralleldisposition of the arms of said bracket and the legs of said framepermitting longitudinal adjustment of said bracket and armature relativeto said frame during assembly, movable contact arm means having contactsurface means and having first and second ends at an angle relative toeach other, means for mounting said first ends of said contact arm meanson armature for movement therewith, side arm means having first andsecond ends at an angle to each other, means adjustably mounting saidfirst ends of said side arm means on the outer surfaces of said contactbase means, contact means mounted on said second ends of said side armmeans for cooperating with the contact surface means of said spring armmeans with a spacing therebetween according to S1010? M202 20 a M101where S2 equals the normal spacing between the respective contactsurface means and contact means, S1 equals the excursion of the movableend of the armature, C1 and C2 equal the compliance of the armature andmovable contact arm means, respectively, M1 and M2 equal th effectivemass of the armature and movable contact arm means, respectively, 0;equals the ratio of the length of the armature to the length of thecontact arm means, and where S1 equals at least 501ZS2.

3. A vibratory interrupter comprising a frame having first and secondlegs and a closed end for a substantially U-shaped form having an openend, each of said legs having a shoulder therein, a driver coil, meansfor mounting said coil on said closed end of said frame, contact basemeans having outer surfaces, means for mounting said contact base meansin said frame abutting said shoulders, a bracket arm mounted on andextending across said open end of said frame, an armature having firstand second ends and having a spring hinge portion, means for mountingsaid first end of said armature on said :bracket arm with said secondend of said armature extending toward said closed end of said frame,said secend end of said armature extending in close proximity to saidcoil, first and second spring arms each having a contact surface andhaving first and second ends substantially at right angles relative toeach other, means for mounting said first ends of said spring arms onsaid armature between said second end thereof and said hinge portion,said second end of said spring arms extending away from said closed endof said frame, said contact surfaces being in a plane passingsubstantially through said spring hinge portion and being substantiallyperpendicular thereto, first and second side arms each having first andsecond ends substantially at right angles to each other, meansadjustably mounting said first ends of said side arms on the outersurfaces of said contact base means with said second ends thereofextending away from said closed end of said frame, and contact meansmounted on said second ends of said side arms for cooperating with thecontact surfaces of said spring arms with a spacing therebetween, saidfirst ends of said side arms having a width substantially equal to thespacing between the legs of the U-shaped frame for rigidity and saidsecond ends of said S equals side arms having a width less thanone-third the width of the first ends of said side arms to permitrelatively greater flexibility of said first ends to allow foradjustment by bending of the parallelism between the respective contactmeans and contact surfaces, according to where S2 is the spacing betweenthe contact means and contact surfaces, Si is the excursion of thesecond end of the armature, and a is the ratio of the length of thearmature to the length of the side arms.

4. The method of assembling a vibrator having a U-shaped frame, avibrating reed having a weighted end, and a driver coil with a permeablecore, said method comprising fabricating a reed sub-assembly byfastening movable contact means on said reed and fastening a mountingbracket to one end of the reed, mounting the driver coil on the closedend of said frame with said core extending in the direction of the sidelegs of the frame, placing the reed sub-assembly within the legs of theframe with said mounting bracket at the ends of the legs of the frameand with said reed extending toward said coil, adjusting said reedsub-assembly longitudinally for close spacing with said core of saidcoil and adjusting said reed sub-assembly laterally for an offsetcondition of said reed weighted end and the core of said coil, andsecuring said reed subassembly in place in said frame in said adjustedposition.

5. The method of assembling a vibrator having a U-shaped frame, avibrating reed having a weighted end, a driver coil, a movable contactand a fixed contact, said method comprising fabricating a reedsub-assembly by fastening a movable contact on one side of said reed andfastening a mounting bracket to one end of the reed, mounting the drivercoil on the inner side of the closed end of said frame, placing the reedsubassembly within the legs of the frame with said mounting bracket infrictional engagement with the ends of the legs of the frame and withsaid reed extending toward said coil, the elasticity of said legs ofsaid frame frictionally holding said reed sub-assembly in any desiredposition, adjusting said reed sub-assembly longitudinally and laterallyfor close spacing with said coil and for an offset condition of saidreed weighted end and said coil, soldering said reed sub-assembly inplace in said frame in said adjusted position, adjustably mounting afixed contact on said frame for cooperation with said movable contact,and longitudinally shifting said fixed contact to obtain a spacingbetween said fixed contact and said movable contact less than where S1is the excursion of the weighted end of the reed and a is the ratio ofthe length of the reed to the length of the movable contact.

6. The method of assembling a vibrator having a U-shaped permeableframe, a vibrating reed having a weighted end, a driver coil with apermeable core, cross members, movable contacts and fixed contacts, saidmethod comprising fabricating a reed sub-assembly by fastening first andsecond movable contacts on opposite sides of said reed and fastening amounting bracket to one end of the reed, mounting the driver coil on theinner side of the closed end of said frame with said core extending inthe direction of the side legs of the frame, placing the reedsub-assembly within the legs of the frame with said mounting vbracket infrictional engagement with the ends of the legs of the frame and withsaid reed extending toward said coil, the elasticity of said legs ofsaid frame frictionally holding said reed sub-assembly in any desiredposition, adjusting said reed sub-assembly longitudinally and laterallyfor close spacing with said core of said coil to provide an efficientmagnetic structure with a minimum air gap and for a longitudinal offsetcondition of said reed weighted end and the core of said coil, securingsaid reed sub-assembly in place in said frame in said adjusted position,fastening cross members on said frame each bridging the two legs of theframe on opposite sides of said vibrating reed, insulatingly mounting byan adjusting screw a fixed contact on each of said cross members forcooperation with said movable contacts, and bending and longitudinallyshifting said fixed contacts to obtain parallelism between said fixedcontacts and said movable contacts and to obtain a neutral spacingtherebetween less than where Si is the excursion of the weighted end ofthe reed and a is the ratio of the length of the reed to the length ofthe movable contacts.

7. The method of assembling a vibrator having a U-shaped permeableframe, a vibrating reed having a weighted end, a driver coil with apermeable core, cross members, movable contacts and fixed contacts, saidmethod comprising fabricating a reed sub-assembly by fastening first andsecond movable contacts on opposite sides of said reed substantially ina plane perpendicular to said reed and fastening a mounting bracket toone end of the reed, mounting the driver coil on the inner side of theclosed end of said frame with said core extending in the direction ofthe side legs of the frame, placing the reed sub-assembly within thelegs of the frame with said mounting bracket in frictional engagementwith the ends of the legs of the frame and with said reed extendingtoward said coil, the elasticity of said legs of said frame frictionallyholding said reed sub-assembly in any desired position, longitudinallyadjusting said reed sub-assembly for close spacing with said core ofsaid coil to provide an eflicient magnetic structure with a minimum airgap, laterally adjusting said reed sub-assembly for an offset conditionof said reed weighted end and the core of said coil, dipping the openend of said frame in molten solder to secure said reed sub-assembly inplace in said frame in said adjusted position, brazing cross members onopposite sides of said frame each bridging the two legs of the framenear said vibrating reed, insulatingly mounting by an adjusting screw afixed contact on each of said cross-members for cooperation with saidmovable contacts, and bending and longitudinally shifting said fixedcontacts to obtain parallelism between said fixed contacts and saidmovable contacts and to obtain a neutral spacing therebetween less thanit 50a where S1 is the excursion of the weighted end of the reed and 11"is the ratio of the length of the reed to the length of the movablecontacts.

8. In a vibrator having a vibrating reed and a driver co-il mounted inclose proximity thereto for vibrating one end of said reed, theprovision of a frame carrying said reed and said coil and having firstand second legs defining a U-shape at least at the end carrying saidcoil, said two legs having a width dimension which is large relative tothe thickness thereof, said reed being fiat and the said one end of thereed vibrating in a path generally perpendicular to the plane of thereed and generally parallel to the width dimension of said legs, and apermeable weight on said one end of said reed extending into closeproximity with the two legs of the frame in all positions of vibrationof said Weight to establish a low reluctance permeable path for saiddriver coil.

9. A vibrator, including a permeable frame having first and second legsand a closed end defining a U-shape at least at a first end thereof, avibrating flexible reed having first and second ends, means for mountingsaid reed first end on said frame with said second end extending towardsaid closed end of said frame, a driving system including a driver coilmounted on said first end of said frame and having a permeable coreexsaid U-shaped frame and generally perpendicular to said widthdimension, a permeable weight on the second end of said reed having alongitudinal dimension substantially parallel to said axis, said weightextending into close proximity to the two legs of said frame in allpositions of vibration of said reed for high magnetic efiiciency of thedriving system.

10. A vibrator structure, including a frame, a vibrating reed mounted insaid frame, a movable contact arm carried by and vibrating with saidvibrating reed, said contact arm having a resonant frequency with aperiodic velocity, a relatively fixed contact cooperating with saidmovable contact arm for open and closed conditions as said contact armvibrates, said contact arm having a transient velocity during the opencondition of said contacts, and adjustment means for establishing thetransient velocity less than the maximum of said periodic velocity.

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